Johnson was only too happy to help. Over time he won the confidence of the family and would visit their home up to four times a week under the guise of assisting the boy with his computer.

There he began to maintain a sexual relationship with the autistic child.

After two and a half years of continued violation, the youngster found the courage to speak to his parents and tell them about the abuse.

Police arrested Johnson the next day.

Earlier this month, after more than two years of the matter working its way through the legal process, the victim's parents were among those in the District Court at Brisbane when Johnson was sentenced to five years' jail.

The judge took into consideration pre-sentence custody of 658 days as time already served and a parole eligibility date was set that day.

It was an emotional day for the parents who said they thought the judge had been fair.

"At the end of the day, the conviction is good... if you can get a conviction on a pedophile its better than them walking around," they said.

However, their ordeal is far from over.

The victim has been struggling to deal with the abuse.

He still takes long showers and remains terrified of men who resemble Johnson, particularly those who wear high-visibility vests.

The teenager has been hospitalised in previous years from severe PTSD, and has spent days in a psychosis.

"Clayton took away his childhood innocence," the boy's parents said, struggling to hold back the emotion.

"At the end of the day it will always be in the back of your mind."

They said it would be hard for them to trust anyone again.

"You don't trust anyone," they said.

"It's very emotional; I would hate anyone to ever go through this."

The parents said it was the support of justice staff, friends and family that helped them through the trial process.